UC-NRLF 


bfil      353 


STUDIES  IN  WOOD  DECAY  1.  LABORATORY  TESTS  ON 
THE  RELATIVE  DURABILITY  OP  SOME  WESTERN 
CONIFEROUS  WOODS  WITH  PARTICULAR  RE- 
FERENCE TO  THOSE  GROWING  IN  IDAHO 


University  of  Idaho,  Bulletin  No.l. 


THE  SCHOOL  OF  FORESTRY 

OF 

THE  UNIVERSITY  OF  IDAHO 

P.  G.  MILLER,  Dean 
IHLLETIX  >0.  1 


STUDIES  IN  WOOD  DECAY  I.  LABORATORY 

TESTS  ON  THE  RELATIVE  DURABILITY 

OF   SOME    WESTERN    CONIFEROUS 

WOODS     WITH     PARTICULAR 

REFERENCE    TO    THOSE 

GROWING    IN     IDAHO 

By 
HENRY  SCHMITZ 

and 
A.   S.   DANIELS 


I  MVERS1TY  OF  IDAHO 

Moscow 
July,    1021 


Entered  in  the  Post  Office  at  Moscow.  Idaho,  as  a  University  Bulletin;  Vol.  XVI,  No.  16 


THE  SCHOOL  OF  FORESTRY 

OF 

THE  UNIVERSITY  OF  IDAHO 

F.  G.  MILLER,  Dean 


BULLETIN  NO.  1 


STUDIES  IN  WOOD  DECAY  I.  LABORATORY 

TESTS  ON  THE  RELATIVE  DURABILITY 

OF    SOME    WESTERN    CONIFEROUS 

WOODS     WITH     PARTICULAR 

REFERENCE    TO    THOSE 

GROWING     IN     IDAHO 

By 
HENRY  SCHMITZ 

and 
A.  S.  DANIELS 


UNIVERSITY  OF  IDAHO 

Moscow 
July,   1921 


Entered  in  the  Post  Office  at  Moscow,  Idaho,  as  a  University  Bulletin  Vol.  XVI,  No.  16 


. 


OFFICERS  AND  FACULTY  OF  THE  IDAHO  SCHOOL 
OF  FORESTRY 


ALFRED  H.  UPHAM,  Pn.D President  of  the  University 

FRANCIS  GARNER  MILLER,  M.F Professor  of  Forestry 

and  Dean  of  the  School 

CHARLES  EDWARD  BEHRE,  M.F Associate  Professor 

of  Lumbering 

HENRY  SCHMITZ,   Pn.D Associate  Professor 

of  Forest  Products 

JOHN  B.  TAYLOR,  M.S.F Instructor  in  Forestry 

INSTRUCTORS   IN   ASSOCIATED    DEPARTMENTS 

MARTIN  FULLER  ANGELL,  Pn.D Professor  of  Physics 

COL.   EDWARD  CHRISM  AN Professor  Military  Science 

and  Tactics 

HARRISON  C.  DALE,  M.A Professor  Economics 

and  Political  Science 

FLOYD  W.  GAIL,  Pn.D Associate  Professor  of  Botany 

CUTHBERT  WRIGHT  HICKMAN,  B.S.(Ac,R.) .  .Professor  of  Animal 

Husbandry 

CHARLES  NEWTON  LITTLE,  Pn.D Professor  of  Civil 

Engineering 

FRANCIS  BAKER  LANEY,  PHD.,  B.S.    (M.E.) ..Professor 

of  Geology 

GEORGE  MOREY  MILLER,.  Pn.D Professor  of  English 

EUGENE  TAYLOR,  M.A Professor  of  Mathematics 

CARL  LEOPOLD  VON  ENDE,  Pn.D Professor  of  Chemistry 

ALEXANDER  R.  WEBB,  C.E Assistant  Professor  of  Civil 

Engineering 

JERRY  EDWARD  WODSEDALEK,  Pn.D Professor  of  Zoology 

V.  H.  YOUNG,  Pn.D Professor  of  Botany 

T.  P.  JONES Representative  for  Idaho  of  Pacific  Logging 

Congress 


SPECIAL  LECTURERS  FROM  THE   U.  S.  FOREST   SERVICE 

J.  A.  FITZWATER Lecturer  on  Forest  Management 

C.  K.  McHARG Lecturer  on  Forest  Administration 

C.  C.  DELEVAN..  Lecturer  on  Forest  Protection 


Main  Library 


cs 


STUDIES   IN    WOOD    DECAY    II    LABORATORY    TESTS    ON    THE 

RELATIVE  DURABILITY  OF  SOME  WESTERN   CONIFEROUS 

WOODS  WITH  PARTICULAR  REFERENCE  TO  THOSE 

GROWING  IN  IDAHO. 


HENRY  SCHMITZ  and  A.  S.  DANIELS 

Intelligent  use  is  a  fundamental  concept  of  conservation. 
Thus  the  recent  interest  in  conservation  has  given  an  unusual 
impetus  to  invesigations  making  possible  a  more  rational  utiliz- 
ation of  the  various  species  of  wood. 

Although  information  concerning  the  durability  of  the 
various  American  species  of  wood  is  rather  meagre,  Humphrey  2 
conducted  tests  on  both  the  heart  and  sap  wood  of  a  representa- 
tive list  of  American  woods.  The  results  of  these  experiments 
were  based  upon  single  specimens  of  each  sample  of  wood  and 
may,  therefore,  not  even  be  indicative  of  the  relative  durability 
of  the  various  species  tested  and  since  many  of  the  specimens 
became  too  wet  for  a  fair  test,  comparisons  between  his  results 
and  those  recorded  here  would  be  of  very  little  value. 

The  painstaking  work  of  Zeller  3'  4j  5  marks  the  beginning 
of  a  new  era  in  investigations  dealing  with  the  durability  of 
wood.  Altho  our  results  are  not  entirely  in  accordance  with 
those  found  by  him,  it  should  be  remembered  that  the  species  of 
pine  investigated  in  the  present  study  belong  to  different  groups 
while  those  studied  by  Zeller  all  fall  in  the  hard  pine  group. 

The  work  of  Schmitz  6  indicates  that  there  may  be  a  great 

1  Several  investigations  are  already  in  progress  in  the  Forest  Products  Laboratory, 

University  of  Idaho,  dealing  with  the  decay  of  wood  and  it  is  proposed  to  give 
considerable  attention  to  this  important  line  of  investigation  during  the  next  few 
years.  These  investigations  will  include  studies  on  the  durability  of  the  various 
woods,  the  value  of  certain  chemicals  as  preservatives,  enzyme  action  in  various 
wood  destroying  fungi,  and  various  phases  of  the  general  phenomena  of  wood 
decav.  In  order  to  show  the  continuity  or  relationship  between  these  several 
•R'r  jem-?'  **  is  Pr°P°secl  to  group  them  under  the  general  title  of  "Studies  in 
Wood  Decay,  of  which  the  present  article  is  Number  1. — Henry  Schmitz. 

2  Humphrey,   C.  J.    Laboratory  tests  on  the  durability  of  American  woods  I.   Flask 
tests   on   conifers.      Mycoiogia   <V:    80-92.   pl.l.      1916. 

3  Zeller,    S.    M.      Studies    in    the    physiology    of    the    fungi    II.      Lenzites    saepiaria 

ioen'  wln  sPecial  reference  to  enzyme  activity.  Ann.  Mo.  Bot.  Card.  3:  439-512. 
pl.o-y.  1916. 

4  Ibid   III.      Physical   properties   of  wood    in    relation  to   decay   induced   by   Lenzites 
saepiaria   Fries.      Ibid.    4:    93-164.   pl.9-13.f.l.    Charts    1-11.      1917. 

5  Humidity  in  relation  to   moisture  inbibition  by  wood  and  to   spore  germination   on 
wood.     Ibid  7:   51-74.     1920. 

6  Schmitz,   H.      Studies    in    the   physiology  of  the   fungi  VI.      The    relation   of   bac- 
teria to  cellulose  fermentation  induced  by  fungi  with  special  reference  to  the  decay 
of  wood.     Ann.   Mo.   Bot.   Card,     6;   93-136,      1919. 


48290S 


4      THE  SCHOOL  OP  FORESTRY,  THE  UNIVERSITY  OP  IDAHO 

difference  in  results  obtained  under  laboratory  pure-culture 
methods  and  those  that  would  be  obtained  under  natural  con- 
ditions where  there  is  the  invariable  presence  of  ordinary  types 
of  bacteria.  It  is  therefore  hoped  that  it  will  be  possible  to  con- 
tinue this  work  and  extend  it  to  natural  conditions. 

PURPOSE 

The  purpose  of  the  present  study  is  to  test  the  relative  dur- 
ability under  laboratory  conditions  of  the  more  important  coni- 
ferous woods  found  in  Idaho  with  the  hope  of  extending  the  use 
of  the  so-called  inferior  species. 

METHODS  AJO)  MATEBIALS 

The  species  of  woods  used  in  these  fests  were  selected  be- 
cause of  their  apparent  wide  diversity  of  durability  and  since 
they  represent  the  important  western  commercial  woods.  They 
are  as  follows:  western  white  pine  (Pinus  montlcola  Dougl.), 
western  yellow  pine  (Pinus  ponderosa  Lawson),  Douglas  fir 
(Pseudotsuga  taxifolia  (Poir.)  Britt),  western  larch  (Larix 
occidentals  Nuttall.),  western  red  cedar  (Thuja  plicata  Don.), 
white  fir  (Abies  grandis  Lindley),  and  Engelmann  spruce 
(Picea  engelmanni  Engelmann).  The  western  larch,  Engel- 
mann spruce,  western  red  cedar,  western  white  pine  and  western 
yellow  pine  were  obtained  from  a  local  lumber  yard.  The 
Douglas  fir  and  white  fir  were  donated  by  the  Potlatch  Lumber 
Company,  Potlatch,  Idaho. 

The  fungi  used  in  the  present  study  are :  Polyporus  lucidus 
(Lys.)  Fries,  Lenzites  saepiaria  Fries,  Fomes  pinicola  Fries, 
Merulius  pinastri  (Fries)  Burt,  Polystictus  versicolor  (L.) 
Fries,  Pleurotus  sapidus  Kalchbr,  Echinodontium  tinctorium 
Ellis  and  JLverhart,Trametes  fiini  Fries,  Trametes  earned  (Nees) 
Cooke,  and  Lentinus  lepideus  Fries.  The  cultures  were  obtained 
either  by  the  tissue  method  as  described  by  Duggar  7  or  the  spore 
method  as  developed  by  Zeller  8.  There  is  no  question  as  to  the 
purity  of  the  cultures.  The  stock  cultures  of  the  fungi  are  main- 
tained on  both  hardwood  and  pine  sawdust  and  for  these  experi- 
ments, transfers  were  taken  from  the  pine  sawdust  cultures. 

One  inch  boards  composed  entirely  of  heart  wood  were 
obtained  and  were  resawed  into  blocks  measuring  24x1x3  inches. 

7  Duggar,    B.    M.      The    principles    of    mushroom    growing    and    mushroom    spawn 
making.     U.  S.  Dept.  Agri.,  Bur.  PI.  Ind.  Bui.  $5.     1-60  pi.  1-7.     1905. 

8  Zeller,  S.  M.    lac.  <&. 


STUDIES  IN  WOOD  DECAY  5 

The  blocks  were  dried  to  constant  weight  in  an  electric  oven  at 
100°C.  and  weighed  to  the  nearest  0.01  gram.  Except 
in  the  case  of  Engelmann  spruce,  ten  blocks  of  each  species  were 
placed  in  each  of  ten  two-quart  Mason  jars  having  a  layer  of 
absorbent  cotton  on  the  bottom.  The  purpose  of  the  cotton  is 
merely  to  absorb  any  excess  moisture  and  thus  insure  a  more 
even  water  supply.  In  the  case  of  Engelmann  spruce,  eight 
blocks  were  placed  in  each  of  ten  two-quart  jars  also  having  the 
layer  of  absorbant  cotton  on  the  bottom.  The  blocks  were 
placed  on  end  in  every  case. 

To  each  jar  250  cc.  of  distilled  water  were  added.  The 
amount  of  water  to  be  added  was  roughly  determined  by  adding 
varying  amounts  of  trial  flashs  so  that  after  sterilization  the 
blocks  and  cotton  were  well  moistened.  In  the  case  of  the  jars 
containing  larch  a  small  amount  of  free  water  remained  when 
sterilization  was  completed.  After  a  comparatively  short  time, 
however,  this  free  water  was  taken  up  by  the  blocks.  After  the 
water  had  been  added,  the  jars  were  carefully  plugged  with  cotton 
plugs  and  sterilized.  Sterilization  was  effected  at  fifteen  pounds 
pressure  for  twenty  minutes.  It  may  be  objected  that  by  this 
method  of  sterilization  certain  volatile  components  of  the  resins 
which  might  be  present  in  the  wood  would  be  driven  off.  Be 
that  as  it  may,  such  very  volatile  components  would  soon  dis- 
appear from  the  wood  on  exposure  to  the  air  and  accordingly 
this  would  not  be  a  deciding  factor  in  the  durability  of  any  par- 
ticular wood. 

The  inoculations  were  made  as  follows:  transfers  from 
sawdust  cultures  of  the  fungi  were  made  to  sterile  hard  agar 
plates.  When  practically  the  entire  surface  of  the  plate  was 
grown  over  with  mycelium,  it  was  cut  by  means  of  a  sterile 
scalpel  into  small  squares  with  an  area  of  approximately  one 
square  centimeter.  With  a  very  few  exceptions,  a  single  square 
was  added  to  each  of  the  culture  jars.  An  effort  was  made  to 
locate  the  inoculum  in  the  center  of  the  group  of  blocks.  The 
fact  is  of  course  appreciated  that  by  this  method  of  inoculation 
the  blocks  in  the  center  of  the  group  may  become  infected  first 
and  may  be  well  along  the  road  to  decay  before  the  mycelium 
comes  in  contact  with  the  blocks  in  the  periphery  of  the  group. 
When  wood  specimens  are  subjected  to  decay  under  laboratory 
conditions,  there  is  usually  a  great  diversity  in  the  results  for  any 


6      THE  SCHOOL  OF  FORESTRY,  THE  UNIVERSITY  OF  IDAHO 

given  wood.  This  is  true  whether  the  individual  specimens  are 
in  different  culture  jars  or  in  the  .same  culture  jars.  The  reasons 
for  this  variation  are  not  definitely  known  and  it  may  merely  be 
the  law  of  "chance"  that  determines  whether  or  not  infection 
takes  place.  Whatver  it 'be,  "chance"  or  any  other  factor,  that 
influences  the  possibility  of  infection  it  must,  a  priori,  largely 
determine  the  resistance  to  decay  of  any  specific  wood.  How- 
ever, since  the  cultures  were  incubated  for  almost  one  year  and 
since  the  average  of  ten  blocks  was  taken  in  each  case  except  in 
that  of  Engelmann  spruce,  where  an  average  of  eight  was  taken, 
it  is  felt  that  this  fact  offers  no  serious  objection. 

After  inoculation  the  culture  jars  were  incubated  for  a 
period  of  10.5  months  at  room  temperature.  It  was  found  neces- 
sary to  water  the  blocks  several  times  during  this  period.  When- 
ever this  was  done,  sterile  distilled  water  was  added  and  every 
effort  was  made  to  have  the  moisture  conditions  in  all  of  the 
culture  "flasks  as  nearly  the  same  as  possible. 

After  the  period  of  incubation,  the  blocks  were  again  dried 
to  constant  weight  in  an  electric  oven  at  100° C.  and  weighed. 
The  difference  in  weight  in  the  two  weighings  represents  the 
amount  of  decay.  The  results  for  the  ten  blocks  in  each  jar  were 
averaged  and  the  percent  loss  in  weight  calculated  on  the  basis 
of  the  dry  weight  of  the  wood. 

EESULTS 

In  Table  I,  the  average  loss  in  weight  percent  of  ten  blocks 
after  ten  and  one  half  months'  incubation  at  room  temperature  is 
given. 


STUDIES  IN  WOOD  DECAY  7 

TABLE  I. 

Showing  average  loss  in  weight  in  per  cent  after  ten  and  a  half 
months'  incubation  wh^n  subjected  to  the  action  of  the  various 
fungi  indicated. 


Fungus 

4> 

j* 

<U 
G 

PH 

£ 

0 

0 

| 

£ 

rt 

"Si 
1 

£ 

,£5 

u 

a 

H-l 

9 

13 

3 

i 

iT 

£ 

o 

o 

3 

a, 
t/3 

*c3 

!-s~ 

~1.1 

zn 

1. 

Polyporus 

14  1 

3  9 

5  5 

5  7 

0  2 

3  5 

4  1 

5  3 

2. 

Lenzites 
saepiaria    

.50.5 

30.0 

11.8 

5.4 

0.3 

10.6 

9.8 

16.9 

3. 

Fomes 
pinicola 

28  1 

11  6 

6  7 

7  7 

0  4 

11  3 

9  3 

10  7 

4. 

Merulius 
pinastri      .    .  . 

3  7 

3  8 

3  1 

* 

0  3 

2  3 

1  2 

2  4 

5, 

Polystictus 
versicolor     

2  3 

3  1 

1  5 

4  5 

0  5 

1  3 

2  3 

2  2 

6. 

Pleurotus 
sapidus      

9  4 

3  4 

5  1 

5  1 

0  3 

2  2 

3  1 

4  0 

7. 

Echinodontium 

5  6 

3  6 

4  6 

6  2 

0  4 

4  1 

3  8 

4  0 

8. 

Trametes 
pini      

3  8 

2  2 

3  g 

7  5 

0  2 

1  4 

2  3 

3  0 

9. 

Trametes 
carnea 

10  2 

17  4 

12  2 

8  4 

0  3 

2  0 

3  9 

7  8 

10. 

Lentinus 
lepideus    

33.0 

39.2 

15.8 

7.3 

0.4 

1.2 

10.6 

15.3 

1  1 

Control 

0  3 

0  3 

0  2 

0  4 

0  3 

0  3 

0  3 

i 

\verage  loss  in  weight 
(all     fungi) 

16  1 

'11  8 

7  0 

6  4 

0  3 

4  0 

5  0 

7  2 

*   This  flask  broken  by  accident. 

A  study  of  the  results  tabulated  in  Table  I  brings  out  some 
very  interesting  points  not  only  relative  to  the  various  woods 
but  relative  to  the  action  of  the  various  fungi. 

Under  the  conditions  described,  the  average  loss  in  weight 
in  the  woods  used  due  to  the  action  of  the  fungi  is  7.2%.  Only 
white  pine  and  western  yellow  pine  lost  more  weight  than  this 
general  average.  Douglas  rim  represented  approximately  the 
average  loss  in  weight  and  western  larch,  Engelmann  spruce, 
white  fir,  and  western  red  cedar  are  below  the  average,  in  the 
order  named. 

The  maximum  amount  of  decay  is  caused  by  the  action  of 


8      THE  SCHOOL  OF  FORESTRY,  THE  UNIVERSITY  OF  IDAHO 

Lenzites  saepiaria  on  white  pine  and  the  following  show  less 
decay  in  the  order  named :  Lentinus  lepideus  on  western  yellow 
pine,  Lentinus  lepideus  on  western  white  pine,  Lenzites  saepiaria 
on  western  yellow  pine  and  Fomes  pinicola  on  western  white 
pine.  It  is  significant  that  the  five  highest  rates  of  decay  are 
found  on  western  white  and  western  yellow  pine.  The  fungi 
causing  these  losses  in  weight  are  not  in  any  way  peculiar  to  the 
two  species  of  wood,  but  are  found  generally  on  both  coniferous 
and  the  hard  woods. 

The  results  in  the  case  of  white  fir  are  indeed  interesting. 
Although  this  wood  is  usually  considered  as  being  very  suscepti- 
ble to  decay,  under  the  conditions  of  these  experiments  it  is  only 
surpassed  by  western  red  cedar  in  its  resistance  to  decay.  Even 
Echinodontium  tinctorium,  the  fungus  causing  the  very  prevalent 
brown  heart  wood  rot  of  white  fir,  did  not  cause  even  the  average 
amount  of  decay.  This  may  be  explained  in  part  by  the  fact  that 
the  fungus  grows  rather  slowly.  The  slow  rate  of  growth  of 
Echinolontium  tinctorium  on  hard  agar  and  carrots  has  been 
previously  reported  by  Schmitz  9. 

As  anticipated  none  of  the  fungi  used  made  any  apparent 
growth  on  western  red  cedar.  It  is  evident  from  the  table  that 
the  results  obtained  in  the  case  of  each  fungus  approximate  the 
limit  of  error  as  found  in  the  controls  for  that  species.  The 
cause  or  causes  of  the  durability  of  this  species  will  be  the  sub- 
ject of  further  investigation  in  this  laboratory. 

The  most  desructive  fungus  as  shown  by  the  highest  average 
rate  of  decay  is  Lenzites  saepiaria.  The  physiology  of  this 
fungus  has  been  carefully  investigated  by  Zeller  10.  Lentinus 
lepidus,  Fames  pinicola,  and  Fomes  carnea  follow  in  degree  of 
destructiveness  in  order  named. 

Working  with  various  species  of  pines,  Zeller  n  has  shown 
that  "specific  gravity  or  density  materially  influence  resistance 
to  decay  of  the  heartwood,  i.  e.,  the  more  dense  the  wood,  the 
more  durable  it  is."  However,  this  may  be  within  a  genus,  it  is 
evident  that  it  does  not  necessarily  hold  between  different  genera 
since  the  specific  gravity  of  larch  is  greater  than  that  of  Engel- 
mann  spruce,  white  fir  or  cedar. 

9     Schmitz,    H.     Enzme   action   in   Echinodontium    tinetorium.        Ellis    and    Everhart 
Jour.   Gen.   Phys.  2:   613-616.      1919. 

10  Zeller,  S.  M.     he.  cit. 

11  Zeller,   S.   M.     lac.  cit. 


STUDIES  IN  WOOD  DECAY  9 

The  work  of  Zeller  13  also  indicates  that  in  the  case  of  the 
various  species  of  pine  investigated  by  him  that  "the  width  of  the 
growth  rings  furnishes  a  further  index  of  durability,  the  narrower 
rings  showing  more  resistance  to  fungous  attack  than  broad, 
open  rings."  The  results  recorded  in  the  present  paper  indicate 
that  this  relation  need  not  necessarily  hold  between  different 
genera  since  the  samples  of  larch  used  in  the  present  work  had 
an  average  of  32  rings  per  inch  while  white  fir  had  an  average 
of  five  rings  per  inch.  Even  within  the  genus  Pinus,  this  re- 
lation did  not  hold  since  the  western  white  pine  used  had  an 
average  of  26  rings  per  inch  while  the  western  yellow  pine  had 
an  average  of  12  rings  per  inch.  It  is  evident  that  in  this  case 
a  soft  pine  is  compared  with  a  hard  pine  while  the  pines  studied 
by  Zeller  all  belonged  to  the  hard  pine  group. 

As  has  been  said,  the  average  loss  in  weight  induced  by  all 
the  fungi  on  all  the  woods  is  7.2  per  cent.  A  study  of  Table  I 
indicates  that  four  fungi,  namely:  Lenzites  saepiaria  Lentinus 
lep'idus,  Fames  pinicola  and  Fomes  earned  induced  a  rate  of  decay 
above  this  average. 

While  no  direct  study  was  made  relative  to  the  rate  of 
growth  of  the  various  fungi  used,  even  a  cursory  observation 
shows  that  these  four  fungi  are  among  the  more  rapidly  growing 
species.  Although  Echinodontium  tinctorium  and  Trametes  pini 
are  among  the  more  important  forms  causing  heart  wood  rots  in 
the  Northwest  the  average  rate  of  decay  induced  by  them  is  low. 
This,  as  has  been  mentioned,  may  in  part  be  explained  by  the  fact 
that  they  are  relatively  slow  growing  forms.  Even  so,  the  rela- 
tion between  rate  of  growth  and  rate  of  decay  need  not  neces- 
sarily hold,  for  example,  Polystictus  versicolor  has  a  relatively 
rapid  rate  of  growth  but  induced  a  low  rate  of  decay.  Detailed 
information  concerning  the  relative  rate  of  growth  of  the  common 
and  more  important  wood  destroying  forms  would  be  of  great 
practical  and  immediate  importance  in  determining  how  soon 
after  a  fire  or  other  disaster  a  tree  would  become  badly  decayed. 

From  a  technical  and  practical  point  of  view,  it  is  evident 
that  under  certain  conditions,  as  for  example  those  of  these 
experiments,  white  fir  is  not  as  susceptible  to  decay  as  generally 
thought.  When  the  susceptibility  to  decay  of  any  wood  is  con- 
sidered, the  fungus  inducing  that  decay  must  also  be  considered. 

13    Zeller,  S.  M.     he.  cit. 


10    THE  SCHOOL  OF  FORESTRY,  THE  UNIVERSITY  OF  IDAHO 

For  example,  Fomes  pinicola  induced  a  higher  rate  of  decay  in 
white  fir  than  in  Douglas  fir  while  Fomes  earned  induced  a  much 
higher  rate  of  decay  in  Douglas  fir  than  in  white  fir. 

If  the  average  rates  of  decay  are  considered,  the  results  indi- 
cate that  with  the  exception  of  western  red  cedar,  under  the  con- 
ditions of  these  experiments,  white  fir  is  the  least  susceptible  to 
decay  while  western  white  pine  is  the  most  susceptible  and 
Douglas  fir  represents  approximately  the  average  degree  of 
durability. 

It  is  clearly  recognized  that,  however  interesting  the  above 
results  may  be,  before  they  can  be  generally  accepted  it  will  be 
necessary  to  carry  out  similar  experiments  under  natural  condi- 
tions. The  various  species  of  wood  should  be  used  under  similar 
conditions  and  a  careful  study  of  the  results  made.  The  School 
of  Forestry  is  at  present  carrying  on  these  experiments. 


STUDIES   IN  WOOD   DECAY  11 


CONCLUSIONS 

It  would  seem  that,  from  the  results  of  the  preliminary  ex- 
periment above  discussed,  it  would  be  safe  to  conclude  that : 

1.  White   fir  and   Englemann   spruce  may  not  be   as   sus 
ceptible  to  decay  as  generally  thought. 

2.  When  different  genera  are  considered,  the  specific  grav- 
ity of  the  wood  is  not  necessarily  an  indication  of  its  durability. 

3.  Within  the  same  genus,  the  number  of  annual  rings  per 
inch  is  not  necessarily  an  indication  of  the  durability  of  the  vari- 
ous species. 

4.  Certain  fungi  causing  very  prevalent  and  complete  heart 
rots  of  standing  timber  may  not  induce  a  high  rate  of  decay  due 
to  their  slow  growth. 

5.  The  durability  of  any  wood  is  not  only  a  question  of  the 
inherent  properties  of  the  wood  itself,  but  also  depends  upon  the 
species  of  fungi  prevalent  in  any  particular  locality  in  which  the 
wood  is  used. 

6.  Under  the  conditions  of  these  experiments,  western  red 
cedar  is  the  least  susceptible  to  decay,  while  western  white  pine 
is  most  susceptible  and  Douglas  fir  represents  approximately  the 
average  of  durability. 

7.  Experiments  involving  the  use  of  the  different  species 
of  wood  under  natural  conditions  are  necessary  before  final  con- 
clusions can  be  drawn. 


School  of  Forestry 

University  of  Idaho 

Four  Year  Course,  with  opportunity  to  sjJtH-ialize  in  General 
Forestry,  Logging  Engineering,  and  Forest  Grazing. 

Forest  Ranger  Course  of  high  school  grade,  cpvering  two 
years  of  five  months  each. 

Special  Short  Course  covering  twelve  weeks  designed  for 
those  who  cannot  take  the  time  for  the  fuller  courses. 

No  tuition  is  charged  for  any  of  the  above  courses,  and 
otherwise  expenses  are  the  lowest. 

Correspondence  Course.  A  course  in  Lumber  and  Its  Uses 
is  given  by  correspondence  for  which  a  nominal  charge 
is  made. 

Advantages.  Eighteen  National  Forests  are  located  in  Idaho. 
The  total  forested  area  of  the  State  is  23,000,000  acres  and 
the  estimated  stand  is  130,000,000,000  ft.  b.m.  This  in- 
sures an  abundance  of  summer  work  and  unusual  oppor- 
tunities for  final  permanent  employment. 

For  Further  Particulars  Address 

Dean,  School  of  Forestry,  University  of  Idaho 

Moscow,  Idaho 


Gaylord  Eros. 

Makers 

Syracuse,  N.  Y. 
PAT.  JAN,  21,  1908 


YD  02929 


UNIVERSITY  QF  CAUFORNIA  LIBRARY 


